Autophagy plays an important role in maintaining the cellular homeostasis. One of its functions is to degrade unnecessary organelles and proteins for energy recycling or amino-acids for cell survival. Ablation of autophagy leads to neurodegeneration. Multiple sclerosis (MS), a permanent neurological impairment typical of chronic inflammatory demyelinating disorder, is an auto-immune disease of the central nervous system (CNS). Autophagy is tightly linked to the innate and adaptive immune systems during the autoimmune process, and several studies have shown that autophagy directly participates in the progress of MS or experimental autoimmune encephalomyelitis (EAE, a mouse model of MS). Dysfunction of mitochondria that intensively infl uences the autophagy pathway is one of the important factors in the pathogenesis of MS. Autophagy-related gene (ATG) 5 and immune-related GTPase M (IRGM) 1 are increased, while ATG16L2 is decreased, in T-cells in EAE and active relapsing-remitting MS brains. Administration of rapamycin, an inhibitor of mammalian target of rapamycin ( mTOR), ameliorates relapsing-remitting EAE. Infl ammation and oxidative stress are increased in MS lesions and EAE, but Lamp2 and the LC3-II/LC3-I ratio are decreased. Furthermore, autophagy in various glial cells plays important roles in regulating neuro-infl ammation in the CNS, implying potential roles in MS. In this review, we discuss the role of autophagy in the peripheral immune system and the CNS in neuroinfl ammation associated with the pathogenesis of MS.
Keywords: autophagy; multiple sclerosis; neuro-infl ammation ·Review·
IntroductionAutophagy, a lysosome-dependent degradation pathway, contributes to maintaining cellular homeostasis. Clearance of long-lived proteins, unnecessary organelles, and aggregate-prone proteins is mainly executed by autophagy for recycling cellular materials [1] . There are three subtypes of autophagy, macroautophagy, chaperone-mediated autophagy (CMA), and mitophagy. Macroautophagy is the major type for selective degradation of protein aggregates or misfolded proteins. The ubiquitin-labeled proteins are recognized by autophagy receptors, such as p62, neighbor of BRCA1 gene 1 (NBR1), and NIP3-like protein X (NIX), to form autophagosomes that then fuse with lysosomes for degradation. Many autophagy-related genes function during this process, such as Unc51-like kinase (ULK1) and autophagy-related gene (ATG) 5. Mammalian target of rapamycin (mTOR) represses autophagy by regulating ULK1 phosphorylation, while AMPK activates this process.CMA mediates the degradation of large molecular-weight proteins containing the KFERQ motif recognized by heat shock cognate protein of 70 kDa (HSC70). The substrate is then escorted to lysosome-associated membrane protein 2 (LAMP2A) for lysosomal degradation. Mitophagy is responsible for the degradation of damaged mitochondria.Parkin and PINK1 play critical roles in this process [2] . More Neurosci Bull August 1, 2015, 31(4): 435-444 436 attention has been paid to autophagy in the path...